This invention relates to a film cassette and in particular to a cassette for roll film.
Roll film is supplied in cassettes having in their circumferential wall an axially extending slot through which the film is incrementally withdrawn by the camera mechanism from the film coil inside the cassette. The film is wound onto a spool in the camera. When the film length is used up, i.e., when all exposures are made, the film is retracted into the cassette by reversing the film winding direction, and the cassette is then ready to be opened for removal of the film for developing of the same.
Such cassettes are conventionally either constructed as a can having one permanently closed axial end and one open end which is provided with a cover, or else the tubular wall has both of its axial ends open and each of these ends is provided with a separate cover.
The known cassettes of this type have certain disadvantages, including the fact that they require relatively elaborate measures to prevent the entry of light into the cassette where the cover (or covers) joins the tubular wall. Also, the removal of the cover for extraction of the exposed film is not always easy and there is no way to assure that the width of the film slot does not vary. If the slot width varies, this results either in entry of light, or, conversely, in the exertion of a retarding action on the film -- depending upon whether the slot undergoes spreading or compression.